Fix correctness and threading issue in new Manufacturer lookup mechanism. It was...

Fix correctness and threading issue in new Manufacturer lookup mechanism.  It was incorrect because the Manufacturer objects should be registered under the searchNames.  The threading correctness is only an issue in the Manufacturer.get(String) method when the name does not exist.  This is handled by using external locking mechanism.  Added a unit test which exposed the problem looking for the manufacturer "Contrail_Rockets".

git-svn-id: https://openrocket.svn.sourceforge.net/svnroot/openrocket/trunk@1000 180e2498-e6e9-4542-8430-84ac67f01cd8